查看更多>>摘要：Ship pipe layout optimization is one of the difficulties and hot spots in ship intelligent production design.A high-dimensional vector coding is proposed based on the research of related pipe coding and ship pipe route features in this paper.The advantages of this coding method are concise structure,strong compatibility,and independence from the gridding space.Based on the proposed coding,the particle swarm optimization algorithm is implemented,and the algorithm is improved by the pre-selected path strategy and the branch-pipe processing strategy.Finally,two simulation results reveal that the proposed coding and algorithm have feasibility and engineering practicability.
查看更多>>摘要：With the rapid development of marine oil and gas exploitation,the evacuation of offshore platforms has received more attention.First,an experimental investigation of the evacuation process of 120 participants in a real offshore platform is performed,and then simulation results provided by Pathfinder are validated against the measurement results.Second,four typical evacuation scenarios on the platform referring to IMO guidelines are investigated by Pathfinder with the speed values achieved in experiments.The simulation results show that both the utilization of exits and evacuation efficiency of people on the offshore platform need to be further improved.Last,the evacuation routes of people under the four scenarios are optimized,and the improvement of the evacuation performance after the optimization is evaluated by several mathematical indicators.Final results show that the evacuation with the optimized route design prompts the use efficiency of exits and further reduces the evacuation time.The present study provides a useful advice for potentially revising the IMO guidelines in future and provides efficient evacuation strategies for planning the emergency evacuation on offshore platforms.
查看更多>>摘要：To increase efficiency in fierce competition,it is necessary and urgent to improve the standard of production planning for shipbuilding.The construction of curved blocks is the bottleneck to improve the efficiency of shipbuilding.Thus it is a key breakthrough for higher shipbuilding productivity to study the curved block production.By analyzing the scheduling problem in curved blocks production,we propose an intelligent curved block production scheduling method and its system based on a knowledge base,and show the main process of the system.The functions of the system include data management,assembly plan generation,plan adjustment,and plan evaluation.In order to deal with the actual situation and inherit the empirical knowledge,the system extracts some rules to control block selecting,algorithm selection,and evaluation thresholds to build a production decision-making knowledge base in the curved block scheduling system.The proposed knowledge base could be referred and modified by users,especially after a few interactions between the users and the knowledge base.The final assembly plan can be visualized and evaluated to facilitate the observation of plan implementation and effects of the decisions in the process.Finally,the system is verified by a large shipyard in Shanghai using real data and the results illustrate that the proposed method can perform the knowledge-based scheduling for curved blocks construction effectively.
查看更多>>摘要：Large unmanned underwater vehicles can carry big payloads for varied missions and it is desirable for them to possess an upright orientation during payload release.Their attitude can hardly be maintained during and after the phase of payload release.Releasing a payload from the vehicle induces uncertainties not only in rigid-body parameters,e.g,the moment of inertia tensor due to the varying distribution of the masses on board the vehicle,but also in the hydrodynamic derivatives due to the vehicle's varying geometric profile.A nonlinear attitude stabilizer that is robust to these time-varying model uncertainties is proposed in this paper.Stability is guaranteed via Lyapunov stability theory.The simulation results verify the effectiveness of the proposed approach.
查看更多>>摘要：It is one of the responsibilities of the navigation support department to ensure the correct layout posi-tion of the light buoy and provide as accurate position information as possible for ship navigation and positioning.If the position deviation of the light buoy is too large to be detected in time,sending wrong navigation assistance information to the ship will directly affect the navigation safety of the ship and increase the pressure on the management department.Therefore,mastering the offset characteristics of light buoy is of great significance for the maintenance of light buoy and improving the navigation aid efficiency of light buoy.Kernel density estimation can intuitively express the spatial and temporal distribution characteristics of buoy position,and indicates the intensive areas of buoy position in the channel.In this paper,in order to speed up deciding the optimal variable width of kernel density estimator,an improved adaptive variable width kernel density estimator is proposed,which reduces the risk of too smooth probability density estimation phenomenon and improves the estimation accuracy of probability density.A fractional recurrent neural network is designed to search the optimal bandwidth of kernel density estimator.It not only achieves faster training speed,but also improves the estimation accuracy of probability density.
查看更多>>摘要：The present work is aimed at determining the optimal geometry layout of a wave energy converter platform for plate energy harvesting performance.A linear potential fluid theory method was applied to analyzing the interaction between the platform and plate.Three factors of layout geometry were tested and the performance of the plate was analyzed.The methodology of design of experiments was used to confirm factor significance and build response surface model.The 1st order model and the 2nd order model were built to describe the relation between factors and plate performance.The significance of two factors and their interactions were revealed,and an optimal parameter set was found.The wave form in front of the plate confirmed the interactions.It is clear that a wide entrance and enclosing channel for waves can maximize the plate performance.
查看更多>>摘要：When controlling the signal of highway-rail level crossings in the port area,the multi-objective signal optimization model is not applicable due to the cross effect of roads and railways and the priority of incoming vehicles.Therefore,in order to ensure that the inbound truck fleet enters the port directly without being affected by the train when passing through the highway-rail level crossing in the port area,the queuing of vehicles in front of the port needs to be reduced,and the priority should be given to the inbound trucks.Based on the idea of priority on key lanes,this study relies on speed guidance information to guide the fleet to shift reasonably,postpone or early arrive at the railway gate.At the same time,the optimization goal is to minimize the delays at intersections,the number of stops,and the vehicle exhaust emissions.The measured data of road-rail level crossings in Dayaowan Port Area of Dalian were selected,and it was re-developed under the VISSIM environment by serial interface to realize signal optimization control under vehicle speed guidance.The original timing plan,multi-objective timing optimization plan and key lanes priority are given to the optimization scheme for simulation experiments.The results show that the multi-objective optimization scheme and the optimization scheme under the priority of key lanes can generally improve the traffic capacity of road-rail level crossings.Compared with the original plan,the optimization plan under the priority of key lanes reduces the delay by 33.3％,the number of stops is reduced by 25％,and the vehicle exhaust emissions are reduced by 31.3％.It proves the effectiveness of the optimization scheme for highway-rail level crossings in the port area under the priority of key lanes,and it is more suitable for highway-rail level crossings.
查看更多>>摘要：The operation time of external trucks in a container terminal is one of port operation key performance indicators concerned by port operators,external truck operators and related government authorities.With the traffic big data combined with the operation characteristics of the container terminal,the system dynamics method is used to build the simulation model of the operation system for external trucks.The simulation results of the operation time of external trucks are consistent with the actual situation,which provides an effective way to eliminate the"black box"of the operation time of the external trucks.The model can also be applied in multiple scenarios by using the traffic big data,and the simulation results can be adopted by the relevant organizations.
查看更多>>摘要：We studied the interactions between freak wave and bottom-mounted vertical cylinder.The freak wave is generated through linear superposition method which satisfies the definition that the wave height is at least two times the significant wave height.A numerical wave tank is developed based on FLUENT software in which the finite volume method is used for the spatial discretization.Grid sensitivity is conducted in 2D model,and then the freak wave is simulated in 3D model.The freak wave loads on the vertical cylinder are calculated and compared with the results obtained through Morison equation.The numerical results present larger peak and shallower trough compared with the prediction of Morison equation.Meanwhile,the free surface wave elevation within a radius distance around the vertical cylinder is investigated.The lowest wave run-up around vertical cylinder caused by freak wave is about 55％of the highest wave run-up,and the direction is about 45 ° of the wave propagation.
查看更多>>摘要：This paper presents the static and fatigue tests of hybrid(bonded/bolted)glass fiber reinforced poly-mer(GFRP)joints.Nine specimens of single-lap hybrid GFRP joints have been fabricated to study the static and fatigue behaviors in the experimental campaign.The static tests of uniaxial tension loading are first conducted,from which the static ultimate bearing capacities of the joints are obtained.High-cycle fatigue tests are subse-quently carried out so that the fatigue failure mode,fatigue life,and stiffness degradation of joints can be obtained.The measuring techniques including acoustic emission monitoring and three-dimensional digital image correlation have been employed in the tests to record the damage development process.The results revealed that the static strength and fatigue behavior of such thick hybrid GFRP joints were controlled by the bolted connections.The four stages of fatigue failure process are obtained from tests and acoustic emission signals analysis:cumulative damage of adhesive layer,damage of the adhesive layer,cumulative damage of GFRP plate,and damage of GFRP plate.The fatigue life and stiffness degradation can be improved by more bolts.The S-N(fatigue stress versus life)curves for the fatigue design of the single-lap hybrid GFRP joints under uniaxial tension loading are also proposed.
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